I'm using org.apache.commons.fileupload.servlet.ServletFileUpload.ServletFileUpload(FileItemFactory)
and defining the encoding when reading out parameter value:
List<FileItem> items = new ServletFileUpload(new DiskFileItemFactory()).parseRequest(request);
for (FileItem item : items) {
String fieldName = item.getFieldName();
if (item.isFormField()) {
String fieldValue = item.getString("UTF-8"); // <-- HERE